Iran's intelligence ministry said its agents have dismantled a sabotage and terrorism network linked to Israel and Britain.
A statement on the ministry's website said its agents had arrested 12 people who had been preparing to enflame ethnic conflicts in Iran through sabotage and assassination.
The statement said the group had links to Israel's spy agency, the Mossad, through a "reactionary" Arab country in the region.
It said they also had links with Britain and spy rings based on the Indian subcontinent, adding that authorities had confiscated a remarkable amount of weapons in the operation.
The statement did not name the detainees or the time and place of the operation.
From time to time Iran announces that it has dismantled groups linked to the Mossad and western intelligence services.